Household Products Are Now a Major Source of Outdoor Air Pollution in Urban Areas

Air pollution is defined by the World Health Organization as the “the world’s largest single environmental health risk” and causes millions of premature deaths annually. Exposure to air pollution is associated with respiratory diseases (including asthma and changes in lung function), cardiovascular diseases, adverse pregnancy outcomes (such as preterm birth), and even death. In 2013, the World Health Organization concluded that outdoor air pollution is carcinogen to humans. In other words, air pollution is an invisible killer—may not always be visible, but it can be deadly.

The two major types of outdoor air pollution, smog and soot, come from cars and trucks, factories, power plants, incinerators, engines—anything that combusts fossil fuels such as coal, gas, or natural gas. Smog, or “ground-level ozone,” occurs when emissions from combusting fossil fuels react with sunlight. Soot, or “particulate matter,” is made up of tiny particles of chemicals, soil, smoke, dust, or allergens, in the form of gas or solids that are carried in the air.

However, results from a recent study (published in the journal Science) show that in urban areas, chemicals contained in consumer goods such as personal care products, indoor cleaners, paints and pesticides now contribute as much to ozone and fine particulate matter as do emissions from the combustion of fossil fuels.

The study was carried out by a team of government and academic scientists, and focused on a class of chemicals known as “volatile organic compounds,” (VOCs), in the Los Angeles area—notorious for its smog. VOCs easily vaporize and waft into the atmosphere, where they react to produce either ozone or particulate matter. Notably, the VOCs present in many consumer products are meant to escape into the air. The study found that, in some urban areas, household chemicals now contribute fully one-half of emitted VOCs.

The new findings reflect the success of steps taken over the past few decades to clean up car exhaust—as cars get cleaner, and transportation emissions in the United States and Europe decline, the VOCs that form pollution particles increasingly come from consumer products. Study co-author Joost de Gouw said: “It’s worked so well that to make further progress on air quality, regulatory efforts would need to become more diverse. It’s not just vehicles any more.”

The findings do not automatically mean that breathing household VOCs indoors poses a health hazard, as the study was not carried out to address this issue. Rather, they point to the interaction of household VOCs (after they evaporate and are released outdoors) with sunlight and other chemicals in the air such as nitrogen oxides. It’s the resulting chemical reactions that contribute to outdoor air pollution.

Jessica Gilman, a study co-author, said: “Gasoline is stored in closed, hopefully airtight, containers and the VOCs in gasoline are burned for energy. But volatile chemical products used in common solvents and personal care products are literally designed to evaporate. You wear perfume or use scented products so that you or your neighbor can enjoy the aroma. You don’t do this with gasoline.”

The list of household products that produce VOCs includes hundreds of items, perhaps even more. As Gilman told The Atlantic: “The type of products are pretty much everything you would think of if you look under the kitchen sink, on the shelf in your garage, or in your bathroom. They’re soaps, shampoos, lotions, cleaning products, as well as degreasers, adhesives, ink, house paints. You see a single word, fragrances—with that one label, there’s up to 2,000 different VOCs that could be listed as a fragrance.”

The new findings highlight the need to adapt and tailor additional research—and possibly regulations—to the changing pattern of emissions in cities. Accordingly, in a Sciencecommentary that accompanied the VOCs article, Alastair Lewis, a scientist not involved in the study, wrote: “As knowledge of VOC chemistry improves, it will become possible to develop more targeted approaches to reducing impacts. Prioritizing those VOCs with the greatest aerosol formation potential—for example, through reformulation of consumer products—would be one option. Industry sectors that have until now been left outside of VOC emissions controls may, in a cleaner electrified future, receive more direct attention from regulators.”